At one point, the man was sitting in his car and "shaking his steering wheel," she said.

So Ramirez wrote down the license plate number of the man's car. Just a few hours later, a friend told Ramirez about an Amber Alert that had been issued for a 7-year-old girl who had been abducted from her driveway while her mother was unloading groceries.

Ramirez noticed similarities in the car police were looking for and the car of the man she'd noticed at her workplace.

"The car looked the same … and my girlfriend was telling me, 'You should call. You should call,'" she said.

Antioch police said Ramirez's tip helped them identify their suspect.

"And once we learned who he was, we were able to go out and find him at the Antioch marina because we had information that's where he liked to frequent," Lt. Tammany Brooks said.

They went to the marina and arrested David Allen Douglas, 43. Police said they found the missing 7-year-old girl in the back of his car. She was unharmed.

Douglas has confessed to kidnapping, and in a jailhouse interview with the Bay Area News Group, he appeared to show no remorse.

"She was kind of startled, but she just kind of put her hand out and came with me. And then she turned back and said 'Mommy,'" Douglas said, adding: "When I got her in the car, she said she was scared. I said, 'I know, I'm scared, too … ."

He also said the abduction was "a cry for help to get out of a situation."

Douglas is now being held on $4 million bond.

"Timing in child kidnappings is absolutely critical, and sometimes lifesaving, if you pass information on immediately, like it occurred in this case," said former FBI agent and ABC News consultant Brad Garrett.